Earthquake · reviewed by a seismologist
M 2.8md
Earthquake near El Sobrante, CA
No earthquake was likely felt in El Sobrante in the 24 hours to 3:05 am PST (11:05 UTC). The last one was M 2.6, 13 km (8 mi) SSE, at 6:23 pm PST on 1 November 2026, estimated intensity II (weak) in town; 114 felt reports to USGS. Every earthquake near El Sobrante
This page: a magnitude 2.8 earthquake was recorded 4 km (2 mi) east-northeast of El Sobrante, CA, at 6:34 am PDT on 23 October 2021 (13:34 UTC), 10 km deep. 328 people have reported feeling it to USGS.
USGS: 4km ENE of El Sobrante, CA
27 km (17 mi) NNE of San Francisco, CA · 10 km (6 mi) ENE of Richmond, CA
- When
- 6:34 am PDT on 23 October 2021 ()
- Where
- 4 km (2 mi) east-northeast of El Sobrante, CA · earthquakes near El Sobrante
- Magnitude
- M 2.8 (md)
- Depth
- 10 km below the surface
- Felt
- 328 reports · strongest reported intensity III
- Nearest
- Contra Costa County, 28 km ESE
- Nearest mapped fault
- Hayward fault, 13 km from its surface trace — near is not the same as on
- Status
- Reviewed by a seismologist
USGS · last changed by USGS · we first saw it 283 days ago
Earthquake alerts for El Sobrante, CA
Get a notification in this browser when USGS records an earthquake near El Sobrante, CA. No account or email needed.
Alerts are on for .
Not a warning. An alert comes after USGS publishes a quake, usually minutes after the shaking. For early warning use ShakeAlert, through your phone's Wireless Emergency Alerts or the MyShake app.
This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage.
At this magnitude and depth, people at rest would likely notice it out to about 24 km (15 mi) from the epicentre. In El Sobrante, 4 km away, the estimate is intensity III (weak). Estimated from magnitude, depth and distance with the intensity equation USGS Did You Feel It? uses; felt reports, where there are any, are the measurement.
Likely felt in: Pinole 4 km, intensity III · Hercules 4 km, intensity III · Crockett 8 km, intensity III · San Pablo 8 km, intensity III · El Cerrito 9 km, intensity III · Richmond 10 km, intensity III · Benicia 11 km, intensity II · Martinez 11 km, intensity II. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 400 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.8 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 38,000× the energy of this one
- Magna, Utah 2020 M 5.7 27,000× the energy of this one
- Around the size people start to feel M 3.0 2.4× the energy of this one
- This earthquake M 2.8 about 400 lb of TNT
Energy from the Gutenberg–Richter relation (log10E = 1.5M + 4.8), rounded to two figures; bar length is magnitude, which is already a logarithm of energy. Magnitudes of past earthquakes from the USGS catalogue.
For this area
The largest earthquake within 50 km since 2016 was M 4.5 on 2019-10-15 — about 370 times the energy of this one.
Before 2016, the USGS record lists 6 earthquakes of M5 or more within 50 km; the five largest:
- 7.9 The 1906 San Francisco, California Earthquake · 37 km SW of this epicentre
- 6.0 The 2014 South Napa, California Earthquake · 26 km N of this epicentre
- 5.8 The 1980 Livermore, California Earthquake · 46 km ESE of this epicentre
- 5.4 South of Elmira, California · 47 km NE of this epicentre
- 5.3 The 1957 San Francisco, California Earthquake · 41 km SSW of this epicentre
Since 2016: the QuakeIndex catalogue (US, M1.5+), built from the USGS FDSN event service. Before 2016: USGS ComCat, M5+ from 1900. Distances are between epicentres. This is the record, not a forecast.
Where
Epicentre 37.9862, -122.2555. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Contra Costa County, CA | 28 km (17 mi) | ESE | earthquakes near Contra Costa County |
| Solano County, CA | 42 km (26 mi) | NE | earthquakes near Solano County |
| Marin County, CA | 44 km (27 mi) | W | earthquakes near Marin County |
| Alameda County, CA | 48 km (30 mi) | SE | earthquakes near Alameda County |
| Napa County, CA | 58 km (36 mi) | N | earthquakes near Napa County |
| San Mateo County, CA | 64 km (40 mi) | S | earthquakes near San Mateo County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
55 earthquakes have been recorded within 50 km since this one.
- 1.5 4km WSW of Colma, CA
- 1.7 5km WSW of Pacheco, CA
- 1.5 2km NE of Union City, CA
- 2.0 5km W of Yountville, CA
- 2.6 2km SW of Colma, CA
- 1.5 2km S of Alamo, CA
- 2.3 4km NE of Fairview, CA
- 1.6 2km NE of San Ramon, CA
- 1.9 1km NW of Danville, CA
- 1.7 1km WNW of Danville, CA
- 2.0 1km N of Pacifica, CA
- 1.6 6km E of Vallejo, CA
- 1.9 6km E of Vallejo, CA
- 1.6 3km SE of Concord, CA
- 1.6 7km WSW of Lagunitas-Forest Knolls, CA
Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of . QuakeIndex does not forecast aftershocks. When USGS issues an operational aftershock forecast it appears on the USGS event page.
On USGS
- The official USGS event page — the source of record for every value above
- Did you feel it? Report it to USGS — reports go to USGS, not to us
- ShakeMap for this event, when USGS has produced one
QuakeIndex does not issue warnings. For earthquake early warning see ShakeAlert.